Process for the preparation of macromonomers and macromonomers prepared by this process

ABSTRACT

The invention relates to a process for the preparation of macromonomers which carry at least two hydroxyl groups at one end. The process comprises 
     (1) reacting a polyester, polyether, polyurethane, polyurea or polyamide prepolymer which has a number average molecular weight of 300 to 3000, preferably 500 to 2000, and contains an average of one terminal hydroxyl or amino group and at least one carboxyl group per molecule with a diisocyanate to form an intermediate which contains an average of one terminal isocyanate group and at least one carboxyl group per molecule, and subsequently reacting this intermediate 
     (2) with a compound which has a molecular weight of 90 to 800, preferably 120 to 300, and contains at least two hydroxyl groups in addition to a group which is reactive to isocyanate groups, to form a macromonomer which carries an average of at least one carboxyl group and, at one end, at least two hydroxyl groups per molecule.

The invention relates to a process for the preparation of macromonomerswhich carry at least two hydroxyl groups at one end.

Macromonomers are taken to mean relatively short-chain polymers oroligomers which contain, at one end, functional groups which are capableof polymerization, polyaddition or polycondensation.

Macromonomers are used, in particular, for the preparation of graftcopolymers. It is known that polyethers which carry two hydroxyl groupsat one end can be employed as macromonomers. Such polyethers areprepared by initiating the polymerization of alkylene oxides using anacetal or ketal which contains a H-acidic group in addition to theacetal or ketal group. After blocking the terminal hydroxyl groups,polyether-1,2- or -1,3-diols are obtained from the resultant reactionproducts by elimination of the acetal or ketal group (cf., for example,German Offenlegungsschrift 3,025,807).

The above-described process for the preparation of polyethers which canbe employed as macromonomers is associated with relatively high costsand is only suitable for the preparation of macromonomers based onpolyalkylene oxides.

It would be desirable to have available carboxyl group-carryingmacromonomers for the preparation of water-diluteable polymers.

The object of the present invention is to provide a novel process forthe preparation of macromonomers which carry an average of at least onecarboxyl group and, at one end, at least two hydroxyl groups permolecule.

This object is achieved by a process which comprises

(1) reacting a polyester, polyether, polyurethane, polyurea or polyamideprepolymer which has a number average molecular weight of 300 to 3000,preferably 500 to 2000, and contains an average of one terminal hydroxylor amino group and at least one carboxyl group per molecule with adiisocyanate to form an intermediate containing an average of oneterminal isocyanate group and at least one carboxyl group per molecule,and subsequently reacting this intermediate

(2) with a compound which has a molecular weight of 90 to 800,preferably 120 to 300, and contains at least two hydroxyl groups inaddition to a group which is reactive to isocyanate groups, to form amacromonomer which carries an average of at least one carboxyl groupand, at one end, at least two hydroxyl groups per molecule.

The advantages achieved by the invention are essentially that theprocess according to the invention makes possible the preparation ofcarboxyl group-carrying macromonomers in a simple manner and that theprocess according to the invention can be carried out at relatively lowexpense with a very wide variety of readily accessible prepolymers.

The process according to the invention is a two-step process. In thefirst step, a polyester, polyether, polyurethane, polyurea or polyamideprepolymer which has a number average molecular weight of 300 to 3000,preferably 500 to 2000, and contains an average of one terminal hydroxylor amino group and at least one carboxyl group per molecule is reactedwith a diisocyanate to form an intermediate containing an average of oneterminal isocyanate group and at least one carboxyl group per molecule.

Polyesters which are suitable as prepolymers can be obtained, forexample, by polycondensing dialcohols and dicarboxylic acids or reactivedialcohol or dicarboxylic acid derivatives (such as, for example,dicarboxylic anhydrides) by methods which are generally well-known, thedialcohol component and the dicarboxylic acid component being employedin a molar ratio of 1:1 and the polycondensation reaction beingterminated when the molecular weight desired is reached. In order todetermine the molecular weight of a polyester, simple determination ofthe acid number is sufficient. The molecular weight can be calculatedusing the formula ##EQU1## (M=number average molecular weight, AN=acidnumber). The polycondensation reaction can be terminated, for example,by cooling the reaction batch.

Aliphatic, cycloaliphatic (saturated or unsaturated) and/or aromaticdicarboxylic acids preferably having 2 to 14, particularly preferably 4to 12, carbon atoms per molecule or the esterification-capablederivatives thereof (for example anhydrides or esters), for examplephthalic acid, isophthalic acid, terephthalic acid, tetrahydro- andhexahydrophthalic anhydride, endomethylenetetrahydrophthalic acid,succinic acid, glutaric acid, sebacic acid, azelaic acid, fumaric acidand maleic acid, can be employed for the preparation of polyesterprepolymers.

Aliphatic, cycloaliphatic and/or araliphatic dialcohols preferablyhaving 2 to 15, particularly preferably 2 to 6, carbon atoms, such as,for example, glycols, such as ethylene glycol, propanediol, butanediol,2-ethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, neopentyl glycol,2,2-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,2- and1,4-cyclohexanediol, 1,2- and 1,4-bis-(hydroxymethyl)cyclohexane,bis-(ethylene glycol) adipate, ether alcohols such as di- andtriethylene glycol and dipropylene glycol, can be employed for thepreparation of the polyester prepolymers.

Polyesters which are suitable as prepolymers can also be obtained byself-condensation of hydroxycarboxylic acids, preferably hydroxystearicacid.

A further important method of preparing suitable polyester prepolymersis to react a polyester containing an average of two terminal hydroxylgroups per molecule (known as polyester diol below) with a (preferablycyclic) polycarboxylic anhydride, preferably a cyclic dicarboxylicanhydride, at reaction temperatures not exceeding 80° C., in astoichiometric ratio such that polyester prepolymers are produced andwhich contain an average of one terminal hydroxyl group and at leastone, preferably only one, carboxyl group per molecule.

The polyester diols used can be synthesized from the dicarboxylic acidand dialcohol components already described in detail above.

The polyester diols are preferably reacted with a cyclic dicarboxylicanhydride. The reaction with carboxylic anhydrides, which result inprepolymers containing more than one carboxyl group, is less preferred.

In the reaction of the polyester diol with the polycarboxylic anhydride,the stoichiometric ratios between polyester diol and polycarboxylicanhydride are selected (in general one mole of polycarboxylic anhydrideare employed per mole of polyester diol) so that an average of only onehydroxyl group is esterified per polyester diol molecule. The reactionbetween polyester diol and polycarboxylic anhydride is preferablycarried out in an organic solvent, such as, for example, methyl ethylketone or acetone.

It is of course also possible to employ polyester prepolymers which alsocontain ether and/or urethane and/or urea and/or amide bonds in additionto ester bonds in the polymer chain.

Particularly preferred polyester prepolymers are the prepolymers whichcan be obtained as described above by reacting a polyester diol withtetrahydrophthalic anhydride.

Polyethers which are suitable as prepolymers can be obtained by reactingpolyether polyols, preferably polyether diols, with a (preferablycyclic) polycarboxylic anhydride, preferably with a cyclic dicarboxylicanhydride, but particularly preferably with tetrahydrophthalicanhydride, in stoichiometric ratios such that polyether prepolymers areproduced which contain an average of one terminal hydroxyl group and atleast one, preferably only one, carboxyl group per molecule.

Examples which may be mentioned of suitable polyether diols which aresuitable for the preparation of the polyether prepolymers arepoly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(butyleneoxide) glycol and poly(oxtetramethylene) glycol.

It is of course also possible to employ polyether prepolymers which alsocontain ester and/or urethane and/or urea and/or amide bonds in additionto ether bonds in the polymer chain.

Suitable polyurethane or polyurea prepolymers can be obtained, forexample, by reacting hydroxyl or amino group-containing polyurethanes orpolyureas, preferably polyurethanes or polyureas containing two terminalhydroxyl or two terminal amino groups, with a (preferably cyclic)polycarboxylic anhydride, preferably a cyclic dicarboxylic anhydride,particularly preferably tetrahydrophthalic anhydride, to formprepolymers which contain an average of one terminal hydroxyl or aminogroup and at least one, preferably only one, carboxyl group permolecule.

Polyurethanes or polyureas which contain two terminal hydroxyl or twoterminal amino groups per molecule can be prepared by methods which aregenerally well-known by reacting appropriate stoichiometric amounts ofdiisocyanate and dihydroxyl or diamino compounds.

Aliphatic, cycloaliphatic, araliphatic and aromatic diisocyanates,preferably containing 4 to 25, particularly preferably 4 to 16, carbonatoms, can be used for the preparation of the hydroxyl or aminogroup-containing polyurethanes or polyureas. Examples which may bementioned are: isophorone diisocyanate, trimethylene diisocyanate,tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylenediisocyanate, ethylethylene diisocyanate, 1-methyltrimethylenediisocyanate, 1,3-cyclopentylene diisocyanate, 1,4-cyclohexylenediisocyanate, 1,2-cyclohexylene diisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylene diisocyanate, 2,4-toluylene diisocyanate,2,6-toluylene diisocyanate, 4,4'-biphenylene diisocyanate,1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate,1-isocyanatomethyl-5-isocyanato-1,3,3-trimethylcyclohexane,bis-(4-isocyanatocyclohexyl)methane, bis-(4-isocyanatophenyl)methane,4,4'-diisocyanatodiphenyl ether and2,3-bis-(8-isocyanatooctyl)-4-octyl-5-hexylcyclohexene.

Dihydroxyl or diamino compounds which are suitable for the preparationof the hydroxyl or amino group-containing polyurethanes or polyureasare, for example, aliphatic, cycloaliphatic and/or araliphaticdialcohols or diamino compounds having 2 to 15, preferably 2 to 6,carbon atoms, such as, for example, glycols, such as ethylene glycol,propanediol, butanediol, 2-ethyl-1,3-propanediol,2-ethyl-1,3-hexanediol, neopentyl glycol, 2,2-trimethyl-1,3-pentanediol,hexanediol, cyclohexanediol, 1,4-bis-(hydroxymethyl)cyclohexane,bis-(ethylene glycol) adipate, ether alcohols such as di- andtriethylene glycol and dipropylene glycol, ethylenediamine, 1,2- or1,3-propylenediamine, 1,6-hexanediamine, 2-methyl-1,6-hexanediamine,1-methyl-2,4-diaminocyclohexane, 1,3- or1,4-bis-(aminomethyl)cyclohexane, 4,4'-diaminodicyclohexylmethane orsimilar diamines which are known per se.

It is of course also possible to employ polyurethane or polyureaprepolymers which also contain ester and/or ether and/or urethane and/orurea and/or amide bonds in addition to urethane or urea bonds in thepolymer chain.

Polyamides which are suitable as prepolymers can be obtained, forexample, by polycondensing diamines and dicarboxylic acids or reactivedicarboxylic acid derivatives by methods which are generally well-known,the diamines and the dicarboxylic acids being employed in the molarratio 1:1, and the polycondensation reaction being terminated when themolecular weight desired is reached. In this way, polyamide prepolymersare obtained which contain an average of one terminal amino group andone carboxyl group per molecule.

Polyamides which are suitable as prepolymers can also be obtained byreacting polyamides containing terminal amino groups with a (preferablycyclic) polycarboxylic anhydride, preferably with a cyclic dicarboxylicanhydride, particularly preferably with tetrahydrophthalic anhydride, instoichiometric ratios such that polyamide prepolymers are produced whichcontain an average of one terminal amino group and at least one,preferably one, carboxyl group per molecule.

It is of course also possible to employ polyamide prepolymers which alsocontain ester and/or ether and/or urethane and/or urea bonds in additionto the amide bonds in the polymer chain.

Besides the carboxyl and/or hydroxyl or amino groups, the prepolymersused according to the invention must not contain any functional groupswhich are reactive to NCO groups under the reaction conditions used forthe preparation of the macromonomers according to the invention.

The process according to the invention is preferably carried out usingpolyester prepolymers. The process according to the invention is veryparticularly preferably carried out using polyester prepolymers whichcan be obtained by reacting a polyester diol with tetrahydrophthalicanhydride.

In the first step of the preparation of the macromonomers according tothe invention, one of the above-described prepolymers is reacted with adiisocyanate to give an intermediate containing an average of oneterminal isocyanate group and at least one carboxyl group per molecule.

Diisocyanate and prepolymer are preferably reacted in a molar ratio of1:1 to prepare the intermediates desired.

The reaction between diisocyanate and prepolymer must be directed sothat, as far as possible, all the hydroxyl or amino groups or themajority of the hydroxyl or amino groups and, as far as possible, nohydroxyl group or only a very small number of carboxyl groups react withisocyanate groups. This can be achieved, for example, by employingprepolymers which contain carboxyl groups which are as unreactive aspossible to NCO groups and contain hydroxyl or amino groups which are asreactive as possible to NCO groups. As is known, the followingreactivity series can generally be assumed with regard to the reactivityto NCO groups bound to (cyclo)aliphatic molecular fragments: ##STR1##Sterically hindered carboxyl groups may be mentioned as an example ofunreactive carboxyl groups. In addition, the reactivity of carboxylgroups can be reduced by salt formation. Further measures forcontrolling the reaction in the desired direction comprise the choice ofreaction temperature and the choice of reaction time. As a rule ofthumb, it can be stated that the reaction temperature must be reducedand the reaction time shortened as the reactivity difference betweencarboxyl groups and hydroxyl or amino groups becomes less. The reactionbetween prepolymer and diisocyanate is preferably catalyzed bywell-known methods of polyurethane chemistry and is preferably carriedout in organic solvents, such as, for example, methyl ethyl ketone andacetone.

The diisocyanates used are preferably diisocyanates in which theisocyanate groups are bound to (cyclo)aliphatic molecular fragments.Diisocyanates in which the isocyanate groups are bound to aromaticmolecular fragments are only suitable in exceptional cases due to theirhigh reactivity. The diisocyanates employed preferably contain 4 to 25,particularly preferably 4 to 16, carbon atoms per molecule.

The examples of suitable diisocyanates which may be mentioned are:ethylene diisocyanate, tetramethylene diisocyanate, hexamethylenediisocyanate, trimethylhexamethylene diisocyanate, dodecanediisocyanate, diisocyanatodipropyl ether, cyclohexane diisocyanate,diisocyanatomethylcyclohexane, isophorone diisocyanate anddicyclohexylmethane diisocyanate.

Diisocyanates which are preferably employed are isophorone diisocyanate,dicyclohexylmethane diisocyanate, hexamethylene diisocyanate andtetramethylxylene diisocyanate. Isophorone diisocyanate is particularlypreferably employed.

Particularly preferred intermediates are obtained when a polyesterprepolymer which contains a primary hydroxyl group and a terminalhydroxyl group originating from tetrahydrophthalic acid is reacted with(cyclo)aliphatic diisocyanate, preferably isophorone diisocyanate, in anorganic solvent, preferably methyl ether ketone or acetone, at reactiontemperatures lower than 80° C. until the theoretically calculated NCOcontent is reached.

In the second step of the preparation of the macromonomers according tothe invention, the intermediate prepared in the first step is reactedwith a compound which has a molecular weight of 90 to 800, preferably120 to 300, and, besides a group which is reactive to isocyanate groups,contains at least two hydroxyl groups (known as the polyol componentbelow), in stoichiometric amounts (1 mole of the polyol component aregenerally employed per NCO equivalent) such that macromonomers areobtained which carry an average of at least one carboxyl group,preferably only one carboxyl group, and, at one end, at least twohydroxyl groups per molecule.

Polyol components which can be employed are polyols and polyols whichcontain an amino group in addition to the hydroxyl groups, and polyolswhich contain a mercapto group in addition to the hydroxyl groups.Polyols and polyols which contain an amino group in addition to thehydroxyl groups are preferably employed. Examples which may be mentionedof polyol components which can be employed are triols, tetraols,trimethylolethane, trimethylolpropane, ditrimethylolpropane, glycerol,triethanolamine, diethanolamine, 2-amino-2-methyl-1,3-propanediol,2-amino-2-hydroxymethylpropanediol and 2-amino-2-ethyl-1,3-propanediol.It is of course also possible to employ the polyols in the form of theiracetals or ketals. When the reaction is complete, the acetal or ketalstructures which are still retained are eliminated by the action ofacids.

Particularly preferred polyol components are trimethylolpropane andditrimethylolpropane.

The reaction of the polyol component with the intermediate isexpediently carried out in an inert organic solvent (for example methylethyl ketone or acetone) at temperatures from room temperature to about90° C., and can also be catalyzed by methods which are generallywell-known. In this reaction too, it must be carefully ensured that onlyslight reactions between the --NCO and --COOH groups or none at all,occur. This can be achieved, for example, by employing polyol componentscontaining an amino, mercapto or hydroxyl group which is particularlyreactive to --NCO groups. Further measures for controlling the reactionin the desired direction comprise the choice of reaction temperature andthe choice of reaction time. As a rule of thumb, it can be stated thatthe reaction temperature must be reduced and the reaction time shortenedas the reactivity difference between carboxyl groups and amino, mercaptoor hydroxyl groups becomes less.

A preferred embodiment of the second preparation step comprisesinitially introducing the polyol component and slowly adding theintermediate.

The invention also relates to novel macromonomers. The macromonomersaccording to the invention are distinguished in that they can beobtained by

(1) reacting a polyester, polyether, polyurethane, poly-urea orpolyamide prepolymer which has a number average molecular weight of 300to 3000, preferably 500 to 2000, and contains an average of one terminalhydroxyl or amino group and at least one carboxyl group per moleculewith a diisocyanate to form an intermediate which contains an average ofone terminal isocyanate group and at least one carboxyl group permolecule, and subsequently reacting this intermediate

(2) with a compound which has a molecular weight of 90 to 800,preferably 120 to 300, and contains at least two hydroxyl groups inaddition to the group which is reactive to isocyanate groups, to form amacromonomer which carries an average of at least one carboxyl groupand, at one end, at least two hydroxyl groups per molecule.

The macromonomers according to the invention have, in particular, theadvantages that they carry at least one carboxyl group in addition tothe hydroxyl groups, can be prepared in a simple manner, and are highlysuitable for the directed preparation of, in particular,water-diluteable polymers.

The invention is described in greater detail in the example below. Allindications of parts and percentages are by weight, unless expresslystated otherwise.

EXAMPLE First step of the preparation process according to the invention(preparation of an intermediate)

1040 g (1 mol) of a polyester diol made from neopentyl glycol and adipicacid and having an OH number of 108 are weighed into a 3-liter four-neckflask fitted with stirrer, thermometer and reflux condenser, and areheated to 80° C. 152 g (1 mol) of tetrahydrophthalic anhydride are thenadded, and the mixture is stirred at 80° C. for 1 hour.

157 g of anhydrous methyl ethyl ketone are subsequently added, and thetemperature is kept at 80° C. for a further hour. 222 g (1 mol) ofisophorone diisocyanate are then added rapidly. As soon as the reactionmixture has become homogeneous, 1 g of dibutyltin dilaurate and 314 g ofanhydrous methyl ethyl ketone are added, and the mixture is stirred at80° C. until the NCO content is constant (1.8 to 2.1% by weight,theoretically 2.2% by weight).

Second step of the preparation process according to the invention (apreparation of a macromonomer)

200 g of di-trimethylolpropane (the amount employed depends on the NCOcontent of the intermediate; 1 mol of di-trimethylolpropane is employedper NCO equivalent) and 540 g of anhydrous methyl ethyl ketone areweighed into a 3-liter four-neck flask fitted with stirrer, thermometerand reflux condenser, and are heated to 80° C. while stirring. As soonas the di-trimethylolpropane has dissolved completely, 1885 g of the 1stproduct are added dropwise over the course of 2 hours via an inletvessel. The mixture is then refluxed (at about 90° C.) until (about 2hours) the NCO content has fallen to below 0.02% by weight. The mixtureis finally concentrated to the solids content of 75% by weight byremoving the methyl ethyl ketone by distillation.

We claim:
 1. A process for the preparation of macromonomers which carryat least two hydroxyl groups at one end, which comprises(1) reacting apolyester, polyether, polyurethane, polyurea or polyamide prepolymerwhich has a number average molecular weight of 300 to 3000, and containsan average of one terminal hydroxyl or amino group and at least onecarboxyl group per molecule, with a diisocyanate to form an intermediatewhich contains an average of one terminal isocyanate group and at leastone carboxyl group per molecule, and; subsequently reacting thisintermediate with a compound which has a molecular weight of 90 to 800,and contains at least two hydroxyl groups in addition to the group whichis reactive to isocyanate groups, to form a macromonomer which carriesan average of at least one carboxyl group and, at one end, at least twohydroxyl groups per molecule.
 2. The process as claimed in claim 1,wherein the prepolymer employed is a polyester.
 3. The process asclaimed in claim 1, wherein the prepolymer employed is a prepolymerwhich contains an average of one terminal hydroxyl or amino group andone terminal carboxyl group per molecule.
 4. The process as claimed inclaim 1, wherein the prepolymer employed is a prepolymer which containsan average of one terminal hydroxyl and one terminal carboxyl group permolecule.
 5. The process as claimed in claim 1, wherein the diisocyanateemployed is a diisocyanate whose isocyanate groups are bound to(cyclo)aliphatic molecular fragments.
 6. The process of claim 1 whereinthe prepolymer has a number average molecular weight of 500 to
 2000. 7.The process of claim 1 wherein the compound has a molecular weight of120 to
 300. 8. The process claim 6 wherein the compound has a molecularweight of 120 to
 300. 9. The process as claimed in claim 1 wherein theprepolymer employed is a prepolymer which contains an average of oneterminal hydroxyl or amino group and one terminal carboxyl group permolecule.
 10. The process as claimed in claim 1 wherein the prepolymeremployed is a prepolymer which contains an average of one terminalhydroxyl and one terminal carboxyl group per molecule.
 11. The processas claimed in claim 1 wherein the diisocyanate is one whose isocyanategroups are bound to (cyclo) aliphatic molecular fragments.
 12. Amacromonomer which carries at least two hydroxyl groups at one endcomprised of the reaction product of a polyester, polyether,polyurethane, polyurea or polyamide prepolymer which has a numberaverage molecular weight of 300 to 3000 and contains an average of oneterminal hydroxyl or amino group and at least one carboxyl group permolecule, and a diisocyanate which forms an intermediate containing anaverage of one terminal isocyanate group and at least one carboxyl groupper molecule, which intermediate is reacted with a compound which has amolecular weight of 90 to 800 and contains at least two hydroxyl groupsin addition to the group which is reactive to isocyanate groups, wherebya macromonomer is formed which carries an average of at least onecarboxyl group and, at one end, at least two hydroxyl groups permolecule.
 13. The macromonomer as claimed in claim 12, wherein theprepolymer has a number average molecular weight of 500 to
 2000. 14. Themacromonomer as claimed in claim 12, wherein the compound has amolecular weight of 120 to
 300. 15. The macromonomer as claimed in claim12, wherein the compound has a molecular weight of 120 to 300.